Electromagnet construction



June 21, 1960 L. H. FRosT ELECTROMAGNET coNsTRuc'rIoN Filed May 11, 1955HG. I

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United States Patent O ELECTROMAGNET CONSTRUCTION Louis H. Frost, 1231Breton Road, SE., Grand Rapids, Mich.

Filed May 11, 1955, Ser. No. 507,572

4 Claims. (Cl. 317-184) This invention relates to the structure ofmagnets for use with a'lternating current. It is concerned more par--ticularly with a structure which embodies va solenoid or coil, a coreor frame, 'and an :armature arranged to be moved lincident to theenergizng of the coil with alternating current. Sucha structure may beemployed as the motivating force or mover for controlling various anddivers instrumentalities and elements, such as valves, arranged to beopened and closed, relays or other controlling or controlled devices.

In order to obtain a quiet operation and to eliminate chatter, it hasbeen common heretofore to employ what is known as a shading coil in thepole faces of the frame. Such a shading coil acts as a short circuitturn for the flux and produces a flux through the portion of the poleface which the shading coil surrounds which is out of phase with themain flux. This out of phase fiux provides force ,active upon thearmature when the main fiux, incident to the alternating current, ispassing through zero. This minimizes buzzing and chattering of 'thearmature. The shading .coil tends 'to resist themain flux, or as itmight be said, limits the main flux through the shaded varea of the poleface.

The objects of this invention is to provide a structure to more nearlybalance the reluctance of the unshaded magnetic circuit to that of theshaded magnetic circuit. In -accordance with the invention, |this isaccomplished by providing a mechanical gapV for varying the reluctanceof the magnetic circuit which Will function and adjust itself to providean optimum Operating condition or balance of flux through the shaded andunshaded areas of-the-polefface. -In carrying out the invention the un-2,942,164 Patented June 21, 1960 Fg. 2 is a top plan view.

'Fig. 3 is an enlarged elevational view showing the pole face 'andarmature.

Fig. 4 is an enlarged view showing in plan a pole face and illustratingthe shading coil.

Fig. 5 is -a sectional view taken substantially on line 5-5 of Fig. 1illustrating structure of the device.

Fig. 6 is a sectional view 'taken on line 6-6 of Fig. l showing ayielding element for the armature.

Fig. 7 is a view of diagrammatic nature showing the armature seated uponthe pole faces.

The frame of the structure is of U-shape having one arm 1, another arm2, and a connecting bight portion 3. The frame is preferably made up ofa multiplicity of laminations of magnetic material, such as iron orsteel, as illustrated in Fig. 2, held together by suitable rivets 5.Below the bight portion 3, as Fg. 1 is viewed, is 'a mounting bracket 6held by rivets 7 which also pass through the laminations of the frame.

The ends or poles of -the varms 1 and y2 a-re of the overhanging type,as shown in Fig. 3, wherein -i't will be noted that the top of the arm 1extends laterally to the left, as at 10, as Fig., 3 is viewed,presenting an undersurface l11 indicated in dotted lines. The arm 2 issimilarly constructed, the same' extending nwardly to provide anoverhanging portion 12.

On each side of the frame is a bracket, one at 14 and one at '15,secured by rivets 16 which also pass through the laminations of thecore.

Positioned within the frame is the coil or vsolenoid 20. This coil ispositioned to abut against the lbrackets 14 and 15. In order to hold thecoil against the brackets 14 and 15, there are two spring elements 21and 22 spaced relative to each other and disposed between the bightportion 3 and one end of the coil to 'thus constantly urge thecoilagainst the brackets 14 and 15. The purpose of this will presentlyappear.

shaded areas of -the pole face are provided with a contour so that someportions thereof are -in a plane different from the plane of the `shadedarea and thus are spaced from the cooperating part of the armature whenthe armature seats upon, or substantially seats upon, the shaded area.This is preferably accomplished by providing some of the surfaces of theunshaded area at an angle 'relative to the surfaces of the shaded area.

The ultimate structure of 'the electromagnet is simple but 'the mannerin which the simple structure controls the flux circuit is important -inthat the Optimum Operating condition and balance is attained, and it hasbeen found that an elec-tromagnet device constructed in accordance withthe invention produces a heavier pull when the arm-ature is seated thanthe same device, with all other things being equal, will produce withoutthe invention. Thus, the electrom-agnetc device of this invention ismore efficient and size for size, other things being equal, performsbetter than those heretofore.

An electromagnetic device constructed in accordance with the inventionis shown in the accornpanying drawmgs:

Fig. 1 is a side elevational view showing the coil, the frame, thearmature, and illustrating the armature in one position in dotted lines.

V27 is a spring 30 which underlies the armature.

provided with suitable The frame is provided with centrally locatedguides of non-magnetic material, such as brass; one such guide isillustrated at 25 and the other at 26 and these guides are of plate formand are secured to the bight portion 3, as -by means of a bolt 27 (Fig.6). Also secured by the bolt The spring 30 extends transversely acrossthe bight portion 3 and lies |between the springs l21 and 22. The coil20 is contacts 31 for electrical connection.

The armature is of T-shape having a main or stem portion 35 arranged toslide in the guides 25 and 26 and lateral portions 36 and 37 forming thecross bar. The armature is preferably made of a plurality of laminationssuch as magnetic steel or iron held together by rivets 38 and 39. Theoutside pieces of the armature may be heavier than the otherlaminations, and they project in- Wardly and upwardly therefrom asindicated at 40 and 41 and are provided With aligned apertures 42 forattachment to an inst-rumentality to be operated. When the armature isattracted, the stem engages the spring 30 which is flexed so that thecross bar can be drawn substantially flush against the pole faces. Thisstores energy in the spring 30 which provides a force for overcoming theresidual magnetism when the current is inter'rupted to thus move thearmature from the pole faces. The spring also cushions the impact Whenthe armature is attracted. Also, it will be noted that when the magneticforce pulls the armature down, as Fig. l is viewed, the reaction forceson the coil is against the brackets 14 and 15. Since the solenoid orcoil is at all times held against the bracket 14 or 15 there is nopossibility of relative movement of the coil relative to the frame andfurthermore the springs 21 and 22 are not called upon to take thereaction of the forces acting upon the armature.

. sweet There is a shading coil for each pole of the frame, one beingillustrated at 45 and the other at 46 and since they are identical, onlyone is shown `in detail in Figs. 3 and 4. The shading coil is a closedAturn of copper or in'other words, a copper ring as shown in Pig. 4. Thecoil shown is of rectangular Shape having two runs 46a and 47 andconnecting side portions 48 and '49. The pole face is formed withgrooves 50 for receiving the portions 46a and 47 and to hold the shadingcoil in position, some of the metal -of the core is peened over as at51.

To obtain the Optimum balanced condition the unshaded portions, asaforesaid, are contoured to provide a mechanical gap relative-to thearmature. portion, of course, is the portion which lies within theshading coil while the unshaded portions are those lying without theshading coil. The Contour given Vto the unshaded'portions, as shownherein, resides in angular faces 55 and 56. Both pole faces are the sameand have the same reference characters applied. Thus, a mechanical gap57 is provided by the contour 55 and mechanical gap 58 provided by theContour 56. The angle of the faces 55 and 56, as shown herein, is about45 relative to the plane of the pole faces. This angle, however, may bevaried to obtain a balanced condition for particular physical dimensionsand magnetic conditions involved. Moreover, the gap may be provided bydifferently shaped contours.

The shaded When energized the flux attracts the armature and it 1 movesfrom the dotted line position shown in Fig. 1 until the cross bar of theT substantially seats upon the pole fac'es. The fiux path is across thepole faces traveling through the armaturc. The shaded area, that is, thearea within the shading coil, may be larger than the cross sectionalarea of the respective arms 1 and 2 of the frame. Therefore, the areaactually has flux carrying capacity in excess of the frame arms, but theshading coil resists the lfiow of flux therethrough and delays it, so tospeak, so that when the alternating current is passing through zero the=delayed flux holds the armature seated tight thus minimizing oreliminating buzzing or chattering. The provision Vof the mechanical gapin the unshaded portions, in effect,

adds resistance to the fiow of flux in the unshaded areas. Thus, itmight be said it contributes to the shading function serving to balancethe reluctance of .the unshaded magnetic circuit to that of the shadedmagnetic circuit. As stated above, an electromagnetic device thusconstructed produces a pull on the armature when the armature is .seatedgreater than a magnetic device wconstructed without the invention,otherithings as to mechanical structure and magnetic conditions beingequal.

I claim:

1.*1An electrornagnetic device for use with alternating electricalcurrent comprising, a coil ar'ranged to be supplied with alternatingelectrical current, a frame member formed of magnetic material disposedin proximity to said coil and having a pole face, a movable armaturemember disposed in magnetic proximity to said coil and frame, saidarrnjaturev member being arranged togjbe' moved by magnetic force havingits source in said coil and frame, said armature member having a face, ashadi'ng coil in said face of one of said members defining a shaded areawithin the lshading -coil and `an funshadedgarea outside of the shadingcoil, the other of said facesv and said shaded area having complementaryconforrnation so that said Shader] area is engagable throughout themajor portion of its area with said other face, said unshaded area andsaid other face having surface portions With complementary conformationsso that said surface portion of said 'unshaded area is engaga'blethroughout the major part of its area With said other face portion, thesurface of one of said faces being sloped so that a tapering gap isoprovided between another portion of said unshaded area and the area ofthe face apposed thereto when vsaid armature memberv face substantiallyseats on said frame member face. i

2. The device defined in claim l wherein said shaded area is engagablethroughout substantially ,its entire extent with said other face. v

3,. The device defined `in claim 1 wherein the interen'- gagableportions of said shaded area and other face .are substantially planarand said -interengagable portions of said unshaded area and other face'are substantially planar.

4. The device defined in claim 3 where'in said 'substantially planarportions of said shaded area and 'unshaded area lie substantially in thesame plane.

References Cited in the lfile of this patent UNITED sTATEs PATENTS, i

